Low-frequency permittivity of spin-density wave in (TMTSF)₂PF₆ at low temperatures

Conductivity and permittivity epsilon of(TMTSF)(2)PF6 have been measured at low frequencies of (10(2)-10(7) Hz) at low temperatures below the spin-density wave (SDW) transition temperature T-p. The temperature dependence of the conductivity shows a deviation from thermally activated behavior at T less than or equal to 2 K and a transition to hopping type conductivity. The frequency dependences of Re epsilon = epsilon' and Im epsilon = epsilon '' show log f scaling as it is typical for various disordered systems. The temperature dependence of epsilon' exhibits a maximum which shifts to lower temperatures with decreasing frequency. The temperature variation of the relaxation time has two branches : with decreasing temperature the long-time branch diverges near some temperature (alpha relaxation), while the short-time branch increases monotonically (beta relaxation). The results obtained provide evidence for a transition of the SDW conductor into a glassy-like state at low temperatures similarly to the case of charge density waves.